Construction and earthmoving equipment, as well as many other types of machines, are commonly used in a wide variety of applications. Generally, a machine is powered by an internal combustion engine. In order to enhance the performance of the machine, the engine must perform as efficiently as possible. Because many machines are powered by internal combustion engines, various methods have been developed to increase internal combustion engine efficiency. One method has been to incorporate a two-stage or twin-compressor turbocharger into the internal combustion engine. The turbocharger may compress air prior to entering an engine intake or combustion chamber. Supplying the engine intake with compressed air (“charge air”) may allow for more complete combustion. This may result in improved power density and better engine efficiency. However, compressing the air may also cause an increase in the intake air temperature. Supplying the engine intake with such heated charge air may lead to an undesirable increase in the amount of emissions exiting from the engine. Also, because engines generally produce large quantities of heat already, adding heated charge air to the engine intake or combustion chamber may increase the operating temperature of the engine, thus resulting in excessive wear on engine components.
An air-to-fluid intercooler may be disposed between a first stage compressor and a second stage compressor of the twin-compressor turbocharger and be used to reduce smoke and other engine emissions, such as, nitrous oxides, by cooling the charge air from the first stage compressor before it enters the second stage compressor and, ultimately, the engine intake manifold. Using the air-to-fluid intercooler may also result in lower combustion temperatures, thus improving engine component life by reducing thermal stress on the engine and increasing engine power output. Also, disposing the intercooler between the first stage compressor and second stage compressor may increase the component life and efficiency of the second stage compressor.
The air-to-fluid intercooler may include one or more passages configured to direct flow of heated charge air. The passages may contain heat transfer enhancements, such as, one or more fins, dimples or other surface modifications. The passages may be coupled to an annular tube body configured to direct flow of some type of cooling fluid, for example, a liquid coolant, which may cool the passage. As the heated charge air passes through the passage, it may come into contact with the heat transfer enhancements, such as, fins, of the passage body. Heat may be transferred from the charge air to the fins of the passage, and then from the fins into the liquid coolant, thus removing heat from the charge air.
The flow of charge air from the first stage compressor may enter the air-to-fluid intercooler in a swirling motion. As the flow of charge air enters the passages of the air-to-fluid intercooler, the fins of the passages may disrupt and change the flow direction of the charge air, resulting in a pressure drop of the charge air and ultimately poor engine performance. Also, radial and axial space and size limitations may exist because the air-to-fluid intercooler may be disposed between the first stage compressor and the second stage compressor. Therefore, the heated charge air may flow in the passage of the air-to-fluid intercooler for an inadequate duration resulting in poor heat exchange performance.
One method of improving the performance of an air-to-fluid intercooler under such conditions is described in U.S. Pat. No. 7,278,472 (the '472 patent) to Meshenky et al., issued on Oct. 9, 2007. The '472 patent describes a heat exchanger used as an intercooler in a combustion air charging device such as a turbocharger or a supercharger. The heat exchanger is disposed in a housing and between a compressor wheel and an outlet. The heat exchanger has a donut-shaped core. The core includes a gas flow path with a substantial radial extent and a gas inlet in fluid communication with the compressor wheel and a gas outlet in fluid communication with the housing outlet. A coolant flow path is provided in the intercooler in heat exchange with the gas flow path and has a substantial axial extent. Flattened tubes are also employed in the core and are arranged tangential to a circle concentric with the center for the core. The canting of the flattened tubes is against the direction of swirling charge air flow entering the intercooler and provides a smoother transition of the air flow into the spaces between the tubes to minimize turning losses of the air flow, and thereby reduce pressure loss.
Although the intercooler of the '472 patent may improve performance of an air-to-fluid intercooler, it may have limitations. For example, because of the canted configuration of the flattened tubes, the swirling flow of charge air will still be disrupted. The passages created by the flattened tubes will not accommodate the swirling direction of the charge air as air flow and direction would be interrupted by the tangential walls of the tubes, ultimately resulting in a pressure loss. Also, the passages formed by the tubes do not create adequate air flow length for charge air to flow and undergo cooling.
The air-to-fluid intercooler of the present disclosure is directed towards improvements in the existing technology.